The thing missed in all the "short arm" talk, is that height also matters.

There are a number of good pass rushers in the league with short arms, and most of them are short (relatively speaking). Jared Allen is an exception.

Tackles (especially left tackles) tend to be quite tall, and have long arms. These are the guys that Ingram will have to be able to beat. Football is a game of leverage. A guy with long arms can extend and lock a guy out. One caveat though, this is much easier to do when your arms are extended parallel to the ground. The further you have to reach down, the less effective you are blocking a guy out, and the shorter your reach becomes.

Ingram is only 6'1", while many LT's are 6'6" and taller (Gaither is 6'9"). Melvin also runs with a low center of gravity, which makes him an even lower target. For a big tall guy to reach down low and move his feet quick enough to deal with a guy like Ingram is not easy. The man with the better leverage wins.

While Ingram's 31.5" arms are less than ideal, they aren't as big a handicap because of his power, quickness, and relative shortness. Dumervil has 32" arms, and is only 5'11"..... that works to his advantage with taller tackles. I don't see any reason while Ingram can't have similar success, as long as he stays healthy.